Dewaxing and partially decolorizing petroleum lubricating stock



C. F. TEARS July 2s, 1936.

DEWAXING AND PARTIALLY DECOLORIZING PETROLEUM LUBRICATING STOCK Filed July 16, 1935 CLAUDE E f/RS INVENTOR BY QUJ ATT [(QBIEY Patented July 28, 1936 PATENT OFFICE DEWAXING AND PARTIALLY DECOLORIZ- ING PETROLEUM LUBRICATING STOCK Claude F. Tears, Warren, Pa., assignor to The v Petroleum Processes Corporation,

Wichita,

Kans., a corporation of Kansas Application July 16, 1935, Serial No. 31,567

7 Claims.

'I'his invention relates to the dewaxin and decolorizing of petroleum lubricating stocks.

Particular objects of the invention are to simplify and reduce the costs of these operations; to reduce the number of steps or stages required for accomplishing these particular purposes; to eliminate the requirement forV certain preliminary treatment heretofore found necessary; to accomplish finer or closer separation between oil and waxy layers and to effect all these new and desirable results in a thoroughly practical way.

Other objects and the details of construction and operation by which such objects are attained are set forth in detail or will appear in the course of the following specification.

In operation of the processes disclosed in the Tears Patents Nos. 2,000,427 and 2,008,570, it was found that these had certain advantages for processing heavy residual lubricating stock such as steam refined stock and long residuum from Pennsylvania crude, which did not appear in the original work on the subject. In known dewaxing processes, it is the usual practice to operate on a, charging stock that has been partially decolorized-or acid treated, or de-asphaltized, or to operate cn a distillate stock such as would be obtained by vacuum distillation of topped crude. 'I'he charging stock in other words has normally been subjected to some preliminary treatment for removal of color bearing constituents, asphalt and inhibitors which prevent the formation of wax structures that can be separated from the oil by known means.

In conventional refinery practice, that is, when wax is removed by cold settling or by centrifuging, it is always essential to decolorize before dewaxlng. In the usual cold settling operation, a product that has not been decolorized will not settle to give satisfactory separation of wax and oil. In Vdewaxing by centrifuging, an undecolorized stock results in a wax formation of such consistency that it can not be discharged satisfactorily from the centrifuge bowl.

In the more modern types of dewaxing processes the same procedure as to preliminary treatment is adhered to. In the Bray patents, of which No. 1,949,989 is typical, residual oil is deasphaltized by preliminary treatment with propane at elevated temperature before being dewaxed. In the IGF English Patent No. 389,113 the same procedure is followed` In the Standard Oil French Patent No. 739,264 and English Patent 409,110, the operation is described as applied to the separation of the parafn from a distilled and treated lubricating oil which has been obtained. from crude Mid-Continent petroleum. In the Voorhees Patent 1,862,784, the wax bearing oil is referred to as a treated wax bearing overhead lubricating cu In the Giles Patent 1,943,236, the charging stock is referred to as a residual treated steam refined oil or it may be an overhead lubricating stock. In Haylet Patent 1,968,392 acid treatment and dewaxing are carried out in propane solution with the acid treatment before the de- Waxing stage. In the Tears Patent 2,000,427, high melting point wax is produced by cold settling under pressure from petrolatum stock, which is a filtered or partially decolorized product. In Tears Patent 2,008,570, it is stated by extreme decolorization and removal of crystal forming inhibitors removed by decolorization, lterable wax may be formed. In the Tears Decolorizing and dewaxing petroleum lubricating oils Patent 2,008,569, an outline of conventional refinery practice is given, wherein it is stated that the heavier cylinder stocks or steam refined stocks and long residuum are decolorized before dewaxing. These references show that in the present state of the art the charging stock to known dewaxing processes is subjected to some sort of preliminary treatment before dewaxing.

It has now been established that by modification of the operations described in Tears Patents Nos. 2,000,427 and 2,008,570, including changes in the proportion of solvent to oil before the pressure is applied for settling, residual lubricating oil stocks may be handled without preliminary treatment and with the surprising advantage that the dewaxed oil produced from the opera- 5 tions is largely decolorized.

The wax produced from the operation is of extremely dark color because of the color bearing 'constituents of the original oil accompanying the settled wax.

As an example of the operation, a charge of regular Pennsylvania steam refined stock having a viscosity of 140 seconds at 210 F. Saybolt was dewaxed without prior decolorization. The dewaxed oil represented 80% of the original charge and had a pour test of 0 F. The color of the dewaxed oil in 5% naphtha dilution was 41/2 N. P. A. while the original charging stock in 5% naphtha dilution had a color of 61/2 N. P. A. It is estimated that 75% of the color reduction required to make v a 71/2 N. P. A. color bright stock was accomplished in this dewaxing operation. The cast of the oil was also somewhat better than the usual soft Pennsylvania bright stock cast. The wax separated in the operation had a melting point of 119.2 A. S. T. M. and a dark brownish color. It

lubricating stock cast. 'Ihe viscosity of the wax product was 131 at 210 YF. Saybolt, further indication of the segregation of color constituents with the wax layer, since the usual grade of 118- 120 melting point Pennsylvania petrolatum has a viscosity of about 105 at 210 F. Saybolt. In other words,V combination of the color compounds with the Wax results in a viscosity increase in the Y Wax layer. An interesting point is that the Saybolt Universal-viscosity at 210 F. of the dewaxed Y and partially decolorized oilfshowsan increase of f from 10 to 15 seconds over that of thel original Y.

charging stock. This Viscosity is reduced again lto thatV of the original chargingstock when the dewaXed and partially decolorized oil is decolorized to finished color. Y

Another interesting and desirableresult in thefact that the ash test of the undecolorizedY v charging stock was 550 F. open cup, while the dewaxed oil showeda flash of 560 F. and the wax product hadv a ash of 540" F. This-proves 'that this method of. operation has distinctadvantagesV in- .theY improvement'ofV the Uviscosity flash relae tionship fof the n'ished oil. The usual grade of viscosityhbright stock has a 'ash of, 545P`F. tor550'F.,"but the productfrom this operation has a asli of 560F.Yat the same viscosity.

- Anotherproof of color constituent segregation with the wax 'product is found in the Conradson carbon residue of the charging stock, the d ewaxed oil and thewaX. Carbon residue ofthe original stock was` 2.5', of the dewaXed' oil 12.1, and oft-he wax` 2.8. Thisproves removal from the finished oil' of those compounds whichgserve to increase the carbon residue; and which are removed'by' decolorizing filtration" in' conventional renery practice. The yield of dewaxed oil obtained from the original charging stockgcompares favorably with' that obtained ifrom any. other dewaxing process when producing oil of the samepour test; ,The apparatus lnecessary and procedure are generally similar to'those described; in'Patent 2,000,427Y withv the following exceptions: f

- (1)An exchanger 56 is -provided for heat exchange between warm propane and the cold wax freeo'il and propane solution. yThe cold propane so produced is employed forreplacingY propane evaporatedaduring the chillingjstage andfor restoring and increasing the Ysolvent `to oil ratio. The use Vof such exchanger of course reduces the loadon the compressionvsystem and permits of a considerably'lower operating cost. i I 1 (2) A different type of oil draw ofi arrangementV is provided. In thenew arrangement, a swing line carrying a; sample-line', isused instead of the Xed trycock and draw-olf connections employed in the original process. g This provides a more convenientand cheaper installation in that the Ymultiplicity of valves -is avoided. Also it enablescloser separation between the oiland wax 'layers because the draw-off swing line 'can bernovd to anyi desired level. y.'Ihesample line being Aso located 'that it removes theV sample right at"the'point of draw-'oipermits close control of kthe point of withdrawal; In Patent 2,000,427,

petrolatumisv the'charging'stock and it contains from 25 to 75%- of wax.L YWhen operating on residual stock, YtheY Wax eontent'is only from l10 to 20%;' Thisof course, results in a'much-srr'ialler volume of tliewax layer sothe'waxV level is close tofthei bottoni 'of the"settlers.1

.The proportionr of solvent toxchargingstock apparently is quite important and it appears that va largersolvent y ratio 'than' used in the original process is required. Satisfactory results have been obtained with solvent to oil ratios during the settling stage within the ranges of 3.5 .to 1 to 7 to 1. Higher solvent Vratios than these probf ably would be effective. Y

The costofV-decolorizing Pennsylvania steam refined stock to '7l/2 N. P A. bright stock color by conventional percolation iiltration. methods is from 2 to 3 per gallon. The cost of decolorizing the dewaxed and partially'decolorized oil from 10 this process to the same color bright stock is in` the range'of from 1 to 11/2 per gallon. This shows van important saving in the 'matter of cost of decolorization, particularly when it is consid-V available n the art at present and thatA cold set-x20 v Y ming under Pressurees 'employed in tnis'process is the only mannerfin .which it could be'succ'ess:

Vered, that thegarnount of color removal obtained 15 in this process is obtained at no cost.

fullyrem'oved. Vv.Thisis because of the,unusuallyV pasty'or sticky consistency of ther darkfwaxfcomponent which would rapidlyfclog either an vordi'-V 25 naryV filter ora conventional centrifuge. bowlfr It is conceivable however, that special lters orVV centrifuge machinesor other mechanical separe' ratorscould bedeveloped to handle thesepara` tion of the `Waxan'd'color bearing components 30 and the invention .comprehend'sanysuch form of separation. The addition .of lter aid probably would. makeV the mixture-filterableand this type of separation is also comprel'iended.V

The process has been practiced. on' Pennsylvania 351 cru-de lubricating oil stocks which. contain no''or onlyrrelativelyv small 'amounts .lof asphalt and color bearing compounds. .'In applying the process to lubricating oils fromfother crudes'suc'h as Mid-.Continent crude; it may be necessary toi rst remove a kportion o'fthe asphalt content'untiltheV asphalt and color bearing components are about inthe same proportion as inrthePennsylvania j stocks. Y .Y

YApparently the success of this operation vdepende uponv some ailinityfof the wax component for."those constituents of the oil vthat serve to impart the, colorfto the original oil. It may be' that Vsome of Ythese color components are solid orA vsemi-solid under vthe temperatureY conditions in the settling operation Vthus makingitkpossible to separate them withthe wax in-the cold set-Y tling operation.

The range of temperaturesto which the solution Vis to be'chilled, which temzieraturesY dictate the pressure to which the Asettling lVessels are-to be vented,` dependsupon the :desired .pour test ofthe finished oil. This temperature range may be from'Oc F; to minus 45 F; A Y

vIn ithe'accompanying. drawing; there isl illluse y60 be made all Within the true spirit and broad scope 65 of theV invention. f Y i Fig;1 isa diagrammatic, representation of the complete system.

Fig. 2 is a broken side elevationof one ofthe Chillersk .showing in particular theVVV adjustable 70 swing line and sample line construction;

.Fig. 3 is a broken end elevation ofth'eselsam parts.

' lig.` 4 is a broken perspective view ofthe oitalie andlsampling spout at the end of the swingv line'. 75

' The complete combined operation' is effected `in the illustration as follows:

Normally gaseous liquid solvent such as propane, stored in tank 3, is mixed with undecolorized vwax bearing oil from tank 4, by being transferred by pumps and 6, 'through lines 1 and 8, through a mixer to a heater 9. 'Ihis may be a steam coil vheater which will raise the temperature of the mixture to 125 F. to 200 F., sufficient back pressure being maintained to hold the solvent in the liquid state by means such as back pressure valve 65.

The hot mixture is next cooled as by passage through a water cooler I0, and charged through lines II, I2, I3, into the Chillers and settlers I4, I5, IS, in parallel.- VIn this charging operation, they may be filled to 80% of total volume under a pressure of Vapproximately 150 lbs. per square inch,pressure sufficient to hold the propane in the liquid state.

The chillers and settlers are then slowly vented through Vlines I8, I9, 20, down to approximately atmospheric pressure, with the propane vapor passing off through line 2| to the suction side of the compressor 22, which is connected with condenser 23, to liquefy and return the propane to storage through line 24.

During the early stages of this cooling operation, relatively warm propane at a temperature which may range from 60 to 120 F. is introduced from storage tank 3, through lines 25, 26, 21. These lines are shown as entered down into the bottom of the chilling and settling tanks, so as to make this warm propane bubble up through the previously introducedoil solution. This accomplishes an agitation and thorough admixture and serves to maintain the liquid level up to or close to the original level. This admission of warm propane is continued during the chilling operation and until the temperature inthe chillers and settlers is brought down to approximately 30 F. After this temperature has been reached, the desired high level is maintained by adding cold propane at a temperature of approximately 45 F., corresponding to atmospheric pressure, from cold propane storage tank 28 by pump 29 through lines 3-25, 26, 21.

The cold propane storage tank 28 in the illustration, is charged by expanding partially cooled propane from the exchanger 66, into it through lines 30a, 305, 30e, from propane storage 3, under control of expansion valve 3|. Propane vapor resulting from this refrigerating operation is taken off through lines 32--2I and compressed and condensed in the compression system heretofore described and represented at 22, 23.

The solution ratios may vary but the following may be considered as a desirable example: With chillers and settlers of a total full capacityrof 10,000 gallons each, the liquid contained in each tank to 80% total volume would be 8000 gallons. The mixture of propane and undercolorized wax bearing oil charged into the tank to this level would then consist of 6000 gallons of propane and 2000 gallons of oil or a ratio of approximately 3: 1. After the first chilling by evaporation and the addition of warm and then cold propane to further chill and bring the mixture up to the 80 volume level, this ratio of propane to oil remains the same but the temperature of the charge has been reduced to approximately 45 F., which corresponds to atmospheric pressure.

The Chillers are then shut in and filled to full capacity, in the example, 10,000 gallons, with cold propane from tank 28 through pump 291and lines 30-25, 26, 21. This pump may be continued in operation until pressure on the Chillers reaches approximately 60 lbs. whereupon these chilling and settling tanks may be shut in under such pressure (60 lbs.) with a temperature of 45 F. In this closed state, the amount of propane has been increased to 8000 gallons, While the amount of oil remains the same, 2000 gallons, resulting in an increased ratio of propane to oil mixture of 4 to 1. The stirring or agitation of the mixture by entry of the warm and the cold propane and the boiling due to evaporation results in or creates a practically perfectly uniform mixture of oil in propane and solid or semisolid wax and color bearing components ready to settle.

A settling period of from 1 to 4 hours is usually suflicient for the wax and color component content of the solution to drop to the bottom of the tank, the bright stock remaining in solution in the propane as a denite layer above the wax and color layer.

The precipitation of the wax and color results in a much lower propane to wax and color compound ratio in the bottom layer.

In the example under consideration, this may be a 1 to 1 ratio involving 400 gallons of propane and 400 gallons of wax and color, leaving an upper clear liquid layer containing '1600 gallons of propane and 1600 gallons of bright stock, a propane to oil ratio of about 4.8 to 1. l

The chilling of the tanks by venting to the compressor through lines I8, I9, 20, 2|, is preferably gradual, being carried out in the example over a period of not less than two hours. This is because shorter chilling time results in slower and less complete and definite settling of the wax and color component layer.

The adjustable swing line, carrying with it the sample line affords a practical and' convenient means for quickly and accurately determining the level of separation between the oil and the waxcolor component layers. This structure is shown in detail in Figs. 2 and 3, at the rst Chiller, where the swing line is indicated at 6B, rotatably mounted in the stuffing box head 69, and having an angled inner end terminating in a take-0E about 10, and its outer end rotatably coupled at 1I, to the stationary take-olf line 34.

The sample line is indicated at 12, carried by or incorporated in the swing line and as having a valved discharge 13, at the outer end. The off-take spout 10 is shown in Fig. 4 as thinned down toward a plane substantially radial to the axis of rotation to provide a narrow inlet, which will be substantially parallel with all different levels of liquid, enabling a more or less fine discrimination in all liquid level adjustments. This thinned spout'is illustrated as widened along the axis parallel to the axis of rotation to give it the full capacity of the pipe. The sample line is indicated as terminating centrally of the mouth of the spout so as to give an accurate sample right at the center of withdrawal.

A hand lever 14 is shown provided on the exposed portion of the swing line carrying a screw clamp 15, cooperable with a quadrant 1B. This handle serves both as a `medium for adjusting and securing the swing line and in Aconjunction with quadrant 1B, as an indicator for showing the position of the 'swing line within the tank, the quadrant, if desired, being laid off in suitable indications of angle,A height, volume, or other values.A

The swing lines are indicated as equipped with valves 11and the draw-olf lines with valves 18,

i by whichthey may be appropriately controlled'.

After determining 'the' level. off the combined Waxand color bearing component layer .and setting andI securing the swing line at the proper angleto take oi'the oil above this layer, the oil layer may be withdrawn .down to theA waxcolor bearing component layer level through the swing line 68,and the lines 34, 35, 36 and. pump 31 to the oil stabilizer 38, passing throughexchanger 66, where itis in'heat exchange relationship with warm propane Vgoing to the cold propane therein until the pressure exceeds that at instheillustration to generate afpressure of apoperating pressure may be 150 lbs.

whichzthe' wax stabilizer is operated. fThis stabilizer is indicated atV 44, Fig. 1 and its normal To overcome this, .the Chillers and settlers would be heated proximately 225 lbs. at whichpressure the' entirewax color bearing component layers with accompanying propane will discharge through lines 25',.26,121-45 into the Wax Stabilizer. "The oil stabilizer 38 and wax stabilizer 44, are shownas connected at the top by. a vapor line 4.8, v.running tothe discharge side of the compressor 22 and into condenser 23 and whereby the propane vapor is condensed and returnedto the storage tank 3. v I 'f' The'heat required for stripping the propane fromthe oil and the wax color bearing compolnents :is supplied in the illustration by steam coils 41, 48, in the bottoms of the stabilizers and the oil 'and wax and' color componentsr from these two stabilizers vare shown as discharged through lines 49, into'the oil and waxy strippers 5I, 52,.having top propane vapor connec- V tions V53, 2|, to the suction side-of theA compressor vbottom connections 54, 55.

andil and wax and color compound delivery AY'The oil and Waxstrippers 5I, 52;A areA .shown heated by steam coils 56, 51 and serve .toreniove the last tracesfof 'propane from the oil andwax and color bearing component taken froingthe bottoms of the 'oil'A andwax stabilizers. These strippers are operated'at the'pres'surerexisting in the suction line of .the compressor, whicl may be 0 to-15.poundsgauge'pressure.` f '.The roil andthe wax andr fcolorbearing components 'freed of solvent are indicated in the illustration as passedthrough'lines 54,55, from the. strippersv 5 I, V52, `to -vstorage by Ywayof .pumps 58, 59, 'and' the oil'and the wax coolers BUQSI;

Complete settling of wax and color Vbearing compounds canr be effected'in the relatively short period from 1 to V4 hours, after chilling'i` During-the chilling, themixture ratios are controlled by. additions of lwarm. and cold propane ,to restore the originalratio and nally to Vincrease'it before settling. By carryingiout the settling underpressure offv approximate1y"60'lbs. per'square inch, the distnction'betwen thewaxV and color 'bearing lcompo'unds and oil layers i's-deniteandv 'complete enabling production of practically wax system Amay beA developed into alternate use of the chilling and settling-chambers, so asrto gain continuous or semi-continuous operation. .This

Y isfeasible particularly because of. theY relatively short chilling and settling periods required.v V5 The application ofthe pressurefor cold settling by pumping Vthe-Chillers full is advantageous, but as an alternative, pressure may ,becapplied in-other" Ways and without necessarily` pumping thetanks full.. By way of example, a line'62, is shown extending. from the top of l(the propane Astorage tank 3, branched at 63, to theseveral chilling tanks and suitably valved at 64, enabling at :different se'lected levels.

Instead of chilling'the mixture4 by evaporation of a `portion of the solvent as above described, the refrigeration may be accomplished byV 'indirect 20 Vmeans. In this mode ofoperation the tanks may y be completelyffilled with the propane oil solution andV then chilled by utilizing the coils inthe bottomsof the tanks as chilling surfaces. If indirect chilling is employed, the oil Yto propane` ratios, after chilling to -45 F., would preferably be approximately the same as those in the y abovegiven example and the settling Wouldresult in the same ratios in the oil andV wax color bearing component layers. f p A Vl/Thile propane servesv as a particularly satisfactory solvent and diluent, it will Vbe appreciated that other' solvents of like character may be employe'dl and that the use of .this and other Vterms f in V.the description of the example above is not by '35 Way of 1imitation,.except as that intent is clearly indicated. Y

Whatk is claimed is:

1; :The herein Y disclosed Vprocess" of dewaxing and partially decolorizing a previously untreated 40 l lubricating oil? stock. containing nonasphaltic color 'bodies substantiallyY similar in nature to,VV those present inPennsylvania steam rened stock Y which comprises dissolving saidV untreated residual lubricating oil stock vin :liquefied normally 45 gaseous hydrocarbon under pressure, chilling the mixturen to below wax solidii'ication temperatures while maintaining substantially the original ratio of solvent to oil and separating the wax and color bearing componentsin a combined state from the mixture.

Y 2. 'The herein disclosed process of' dewaxing and'at the same time partially decolorizing an untreated yresidual lubricating'oil stock, which comprises mixinga color bearing undecolorized stock which has vnot previously been subjected to decolorizing or aci-d treatment Vinliqueed normally gaseous hydrocarbon under pressure, chilling the mixture toY below wax solidication temperature yand-batch cold settling Ythe wax` and 60 color-bearing'components from the chilled mixture under pressure above'the'normal Vapor pressure of the solventat the V temperature of the chilledmixture. W n

f3. .The herein disclosed 'process vof dewaxing and :at 'the Sametime v partially decolorizing an untreated residual lobricating oil stock, which iomprisesV mixing av color bearing Yhndecolorized and otherwise untreated residual lubricating oil stock with liqueed; normally gaseous hydrocar- "lo bon underv pressure, heatingthe mixture under pressure Vsufliciently to. effect-complete solution, Y coolingthemixture under press-ure to remove the heat introduced for mixingfand dissolving pur-V poses, gradually releasing the pressure to vapor- T f Y ize suflicient of the solvent to chill the mixture to below Wax solidication temperature, adding liqueed normally gaseous hydrocarbon in sucient Volume to substantially maintain the original solvent ratio while so reducing the pressure and increasing the solvent ratio after chilling, and cold settling from the mixture the Wax and color bearing components under pressure above the normal vapor pressure of the solvent at the temperature of the chilled mixture.

4. The process of claim 1 in which chilling of the mixture is eiected by evaporating part of the liquied normally gaseous hydrocarbon and in which solvent evaporated is at least partly replaced by cold solvent and in which cooling of the latter is effected by heat exchange with the chilled oil solution from which the wax and color bearing components have been separated.

5. The process of claim 3 in which the added liquied normally gaseous hydrocarbon is cooled by heat exchange with the chilled oil solution from which the wax and color bearing components have been settled.

6. The process of claim 1 in which the separation of wax and color bearing components from the mixture is accomplished by batch cold settling under pressure in excess of the normal vapor pressure of the solvent at the temperature of the chilled mixture.

7. The process as in claim 2 in which the cold settling under pressure is effected in a closed vessel and in which the oily layer is first Withdrawn from the vessel and heat is then applied to the Wax and color bearing constituent layer to generate suicient pressure in the vessel to expel said layer from the vessel.

CLAUDE F. TEARS. 

